Modern medical technology has produced a number of medical devices which are designed for compression into a small size to facilitate introduction into a vascular passageway and which are subsequently expandable into contact with the walls of the passageway. Among these devices are blood clot filters such as the filters shown by U.S. Pat. No. 4,425,908 to Simon. The Simon filter is a permanent filter which, when once implanted is designed to remain in place. However, recoverable filters have also been developed as disclosed by U.S. Pat. No. 5,370,657 to Irie and U.S. Pat. No. 5,669,933 to Simon et al.
In the past, generally a hook type device has been employed to implant and position the prior art filters within a body vessel, and to engage the removable filters to effect the recovery thereof. The problem with a hook type recovery device is that the filter or other implanted artifact which is either being positioned for implantation or recovered is permitted to pivot about the hook and become misaligned. Once the device is misaligned within a body vessel, recovery is extremely difficult and realignment can often not be achieved without complete removal and subsequent reimplantation. There is also a possibility that damage to a vessel wall can occur from a use of a hook type recovery unit.
In an attempt to improve on prior art transluminal implantation and removal units, gripping devices have been devised which include a plurality of loop type gripping members made integral with a central tube and which extend outwardly at an angle to the central tube. These gripping members are adapted to surround a unit to be implanted or extracted, and an axially displaceable sleeve which surrounds the central tube engages and causes the gripping members to move inwardly. Devices of this type, which are shown by U.S. Pat. No. 5,464,408 to Duc, operate effectively when the artifact to be gripped is a relatively large unit, such as a stent, having an extensive outer surface which can be engaged by the loop type gripping members. However, if the device to be gripped is a shaft or a shaft with a knob which may be attached to a filter, the device can become misaligned and the shaft will move through the loops which form the gripping members.